Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932066Ab2HVIrU (ORCPT ); Wed, 22 Aug 2012 04:47:20 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:56661 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750769Ab2HVIrI (ORCPT ); Wed, 22 Aug 2012 04:47:08 -0400 Date: Wed, 22 Aug 2012 10:47:02 +0200 From: Ingo Molnar To: Ido Yariv Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Shai Fultheim Subject: Re: [PATCH v2 2/2] x86/pat: Avoid contention on cpa_lock if possible Message-ID: <20120822084702.GA21764@gmail.com> References: <1344445299-22142-1-git-send-email-ido@wizery.com> <1344445299-22142-2-git-send-email-ido@wizery.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1344445299-22142-2-git-send-email-ido@wizery.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1746 Lines: 47 * Ido Yariv wrote: > vSMP Foundation does not require to serialize CPA by guaranteeing that > the most recent TLB entry will always be used. > > To avoid needless contention on cpa_lock, do not lock/unlock it if it > isn't necessary. > > Based on work by Shai Fultheim . > > Signed-off-by: Ido Yariv > Acked-by: Shai Fultheim > --- > Changes from v1: > - Use a synthetic CPUID bit and a use static_cpu_has() as suggested by > H. Peter Avnin > > arch/x86/include/asm/cpufeature.h | 1 + > arch/x86/kernel/vsmp_64.c | 10 ++++++++++ > arch/x86/mm/pageattr.c | 30 +++++++++++++++++++++--------- > 3 files changed, 32 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index 6b7ee5f..92303a0 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -97,6 +97,7 @@ > #define X86_FEATURE_EXTD_APICID (3*32+26) /* has extended APICID (8 bits) */ > #define X86_FEATURE_AMD_DCM (3*32+27) /* multi-node processor */ > #define X86_FEATURE_APERFMPERF (3*32+28) /* APERFMPERF */ > +#define X86_FEATURE_NO_CPA_LOCK (3*32+29) /* Serializing cpa is not required */ Patch looks mostly good, but could we please use some more hardware-ish name, instead of referring to a kernel lock? I.e. how would you name it if this was a real hardware feature? Certainly not 'No CPA Lock'. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/